Users are operating portable digital still and video cameras and digital voice recorders for generating personal digital content. Customarily, such appliances record content on removable memory cards. After completing a session of content recording, or when a memory card is filled up, users usually copy the content of the memory card to their personal computer for viewing, listening, editing, printing, archiving, or sharing with others over the Internet or a cellular network or on optical disks. Usually the memory card, or space on the memory card, is then freed and reused for recording additional content.
Often, the recorded content includes personal memories. Such content cannot be reproduced, and therefore must be carefully archived and protected, for decades or even centuries, just like the photo album of grandpa and grandma. While old black & white photos have proven to withstand decades and centuries of storage, digitally-stored content can be destroyed or lost if the hard disk in which they are stored crashes or the storage media deteriorates or becomes inaccessible due to the storage media becoming obsolete; i.e., due to evolution in hardware or protocol standards.
“Digital preservation” is a known discipline for long-term preservation of digital data. Digital preservation uses strategies such as refreshing, where a fresh copy of the data is produced to overcome storage deterioration; migration, where the data is transformed to match a newer protocol or hardware; replication, where redundant copies are produced and stored separately from the original copy; and physical protection against theft, tampering, fire, natural disasters and the like.
Preservation of personal digital content that is originally recorded on flash memory cards is typically done separately from the memory cards, on magnetic or optical disks. This is because the per-megabyte price of flash memory storage is substantially higher than that of magnetic or optical storage. However, magnetic disks will not typically survive more than a few years. Although regular replication of magnetic disk content could extend the life of the stored content forever, many users will fail to strictly follow the required routines. Optical disks generally do not tend to crash, but they require relatively sophisticated procedures for cataloging and accessing their content. Optical disks vary in longevity. Also, the content of optical disks is not accessible in a convenient way, and the quality of optical disks cannot be monitored.
With the falling prices of memory cards, users could use their memory cards as dedicated long-term storage for their recorded content, instead of continually reusing them to record new content. However, the content stored in NAND flash memory cards may deteriorate, and even irreversibly be lost, after a few years, depending on the card design, the flash type, the extent to which the card is used, and the ambient temperature.
Better longevity is offered by one-time programmable (OTP) solid-state memories. Memory cards that use OTP technology offer “write once/read many” (WORM) functionality. In spite of the higher longevity of OTP cards, many users still prefer the flexibility offered by conventional rewritable flash memory cards for selectively erasing unwanted content to free space for additional/new content, or for copying the entire contents to a hard disk or an optical disk and reusing the card for fresh content recording.
It will be appreciated that the need and desire for long-term archiving of recorded content varies greatly according to the nature of the content. For example, pictures and videos taken for experiments or of an unimportant event under poor lighting conditions may be disposable, while pictures taken at a wedding, family event, trip or reunion, as well as pictures of a child, of a rare natural phenomenon, or just pictures of outstanding quality, are considered indispensable. And, along the continuum from disposable to indispensable, there can be many degrees of importance that users may want to decide for themselves. Even within a series of pictures or videos taken at a certain event, there might be some pictures or videos that users would prefer to keep and others that they prefer to delete. Therefore, using OTP cards for both recording content and archiving it may prove unsuitable for many users or under many circumstances.
There is thus a need for solutions for digital preservation of digital content, that are free of the limitations described above.